package com.hmdp.service.impl;

import cn.hutool.core.bean.BeanUtil;
import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import com.hmdp.utils.SystemConstants;
import org.springframework.data.geo.*;
import org.springframework.data.redis.connection.RedisGeoCommands;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.domain.geo.GeoReference;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.*;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    @Resource
    private CacheClient cacheClient;

    @Override
    public Result queryById(Long id)
    {
        //缓存穿透
        //Shop shop = queryWithPassThrough(id);
//        Shop shop = cacheClient
//                .queryWithPassThrough(CACHE_SHOP_KEY,id,Shop.class,this::getById,CACHE_SHOP_TTL,TimeUnit.MINUTES);

        //利用互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);

        //利用逻辑过期解决缓存击穿
        //Shop shop = queryWithLogicalExpire(id);
        Shop shop = cacheClient
                .queryWithLogicalExpire(CACHE_SHOP_KEY,id,Shop.class,this::getById,20L,TimeUnit.SECONDS);


        if(shop == null)
        {
            return Result.fail("店铺不存在!");
        }

        //7.返回
        return Result.ok(shop);
    }

    //创建一个线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //基于逻辑过期防止缓存击穿
    public Shop queryWithLogicalExpire(Long id)
    {
        String key = CACHE_SHOP_KEY + id;

        //1.从redis中读取缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isBlank(shopJson))
        {
            //3.不存在，直接返回空
           return null;
        }

        //4.命中，先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson,RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(),Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();

        //5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now()))
        {
            //5.1未过期，直接返回店铺信息
            return shop;
        }

        //5.2过期，需要缓存重建
        //6。缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);

        //6.2判断获取锁是否成功
        if(isLock)
        {
            //6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try
                {
                    this.saveShopToRedis(id,20L);
                }
                catch (Exception e)
                {
                    throw new RuntimeException(e);
                }
                finally
                {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }

        //6.4返回已过期的店铺信息
        return shop;
    }

    //缓存击穿
    public Shop queryWithMutex(Long id)
    {
        String key = CACHE_SHOP_KEY + id;

        //1.从redis中读取缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //shopJson有三种情况 1.存在，值为正常  2.“”，空值，为了防止缓存穿透设置的   3.null，不存在

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson))
        {
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }

        //判断redis命中的值是否是为了防止缓存穿透设置的空值
        if(shopJson != null)    //即shopJson是空值
        {
            return null;
        }

        //4.实现缓存重建
        //4.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop = null;

        try
        {
            boolean isLock = tryLock(lockKey);

            //4.2判断是否获取成功
            if(!isLock)
            {
                //4.3失败，则休眠并重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }

            //4.4成功，根据id查询数据库
            shop = getById(id);

            //模拟重建的延时
            Thread.sleep(200);

            //5.判断数据库中是否存在，不存在直接返回错误，并在redis中设置一个空值"",防止缓存穿透
            if(shop == null)
            {
                //为防止缓存穿透，设置一个空值在redis
                stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }

            //6.存在，把该数据写入redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        }catch (InterruptedException e){
            throw new RuntimeException(e);
        }finally {
            //7.释放互斥锁
            unLock(lockKey);
        }

        //8.返回
        return shop;
    }

    //缓存穿透
    public Shop queryWithPassThrough(Long id)
    {
        String key = CACHE_SHOP_KEY + id;

        //1.从redis中读取缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);

        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson))
        {
            //3.存在，直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }

        //判断redis命中的值是否是为了防止缓存穿透设置的空值
        if(shopJson != null)    //即shopJson是空值
        {
            return null;
        }

        //4.不存在，查询数据库
        Shop shop = getById(id);

        //5.判断数据库中是否存在，不存在直接返回错误
        if(shop == null)
        {
            //为防止缓存穿透，设置一个空值在redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }

        //6.存在，把该数据写入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);

        //7.返回
        return shop;
    }

    @Override
    @Transactional
    public Result updateByShop(Shop shop)
    {
        Long id = shop.getId();
        if(id == null)
        {
            return Result.fail("店铺id不能为空!");
        }

        //更新数据库
        updateById(shop);

        //删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + id);

        return Result.ok();
    }

    @Override
    public Result queryShopByType(Integer typeId, Integer current, Double x, Double y)
    {
        //1.判断是否需要根据坐标查询
        if(x==null || y==null)
        {
            //不需要根据坐标查询则直接查询数据库
            Page<Shop> page = query()
                    .eq("type_id", typeId)
                    .page(new Page<>(current, SystemConstants.DEFAULT_PAGE_SIZE));
            return Result.ok(page.getRecords());
        }

        //2.计算分页参数
        int from = (current - 1) * SystemConstants.DEFAULT_PAGE_SIZE;
        int end = current * SystemConstants.DEFAULT_PAGE_SIZE;

        //3.查询redis，按照距离排序、分页
        String key = SHOP_GEO_KEY + typeId;
        GeoResults<RedisGeoCommands.GeoLocation<String>> results = stringRedisTemplate.opsForGeo().radius(
                key,
                new Circle(new Point(x, y),
                new Distance(5000)),
                RedisGeoCommands.GeoRadiusCommandArgs.newGeoRadiusArgs()
                        .includeDistance()
                        .limit(end)
        );

//        GeoResults<RedisGeoCommands.GeoLocation<String>> results = stringRedisTemplate.opsForGeo()
//                .search(
//                        key,
//                        GeoReference.fromCoordinate(x, y),
//                        new Distance(5000),
//                        RedisGeoCommands.GeoRadiusCommandArgs.newGeoRadiusArgs().includeDistance()
//                        .limit(end)
//                );

        //4.解析出id
        if(results == null)
        {
            return Result.ok(Collections.emptyList());
        }
        List<GeoResult<RedisGeoCommands.GeoLocation<String>>> list = results.getContent();
        if(list.size() <= from)
        {
            return Result.ok(Collections.emptyList());
        }

        /*
        GeoResult {
        content: GeoLocation { name: "1", point: (116.404, 39.915) },
        distance: Distance { value: 5000, metric: METERS }
        },
         */

        //4.1截取from~end的部分
        List<Long> ids = new ArrayList<>(list.size());
        Map<String,Distance> distanceMap = new HashMap<>(list.size());
        list.stream().skip(from).forEach(result -> {
            //4.1获取店铺id
            String shopIdStr = result.getContent().getName();
            ids.add(Long.valueOf(shopIdStr));
            //4.2获取距离
            Distance distance = result.getDistance();
            distanceMap.put(shopIdStr,distance);
        });

        //5.根据id去查询店铺
        String idsStr = StrUtil.join(",", ids);
        List<Shop> shops = query().in("id", ids).last("ORDER BY FIELD(id," + idsStr + ")").list();
        for(Shop shop : shops)
        {
            shop.setDistance(distanceMap.get(shop.getId().toString()).getValue());
        }

        //6.返回
        return Result.ok(shops);
    }

    //获取锁
    private boolean tryLock(String key)
    {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    //释放锁
    private void unLock(String key)
    {
        stringRedisTemplate.delete(key);
    }

    public void saveShopToRedis(Long id,Long expireSeconds) throws InterruptedException {
        //1.查看店铺信息
        Shop shop = getById(id);
        Thread.sleep(200);

        //2.分装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));

        //3.写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

}
